1.B.25.1.8
Anion-selective OpdK (OccK1 or OpdK) benzoate/vanillate-selective porin (Tamber et al., 2006; Eren et al., 2012; Liu et al. 2012). The structure of the OpdK porin, specific for vanillate and related small aromatic acids, has been solved by x-ray crystallography (3SYS_A). It is a labile trimer with monomers of an 18 β-stranded barrel and with an inner diameter of 8Å (Biswas et al., 2008). Other substrates transported (but less well) include 4-nitrobenzoate, caproate, octanoate, carbenicillin, cefoxitin, tetracycline antibiotics, and carbapenem antibioitics (imipenem and meropenem) (Eren et al., 2012).  Molecular dynamic simulations and mutant analyses have been reported (Wang et al. 2012).